This is what it looks like when you have a Playbook within a Playbook:
You can tell the difference between a Playbook and a Card because of the colored bar at the top.
How to embed a Playbook inside of a Playbook:
Let's say you want Playbook Aardvark inside the Playbook Bear. Click on Playbook Aardvark (the one you want inside) and copy the Playbook URL through the shareable link.
2. Open Playbook Bear and click on "+ New Card" on one of the columns. Add a title to the Card, and paste the Playbook Aardvark URL into Resource URL.
Do not add a description or Snippet to the card.
3. Click Save. The Playbook Aardvark should appear as a Card on Playbook Bear.